Oxygenators are used to oxygenate the blood of patients during surgical procedures. This is accomplished during the extra-corporal circulation of the blood. The oxygenators typically used are in the art are of various types and can be generally classified as blood film oxygenators and membrane oxygenators. Typical apparatus used by workers are cylinder oxygenators, network oxygenators, bubble oxygenators and disk oxygenators.
Disk oxygenators have been known since the 1950's and are based on the same functional principles as the older type cylinder oxygenators. These disk oxygenators are made up of a large glass blood reservoir in the shape of a tubular cylinder. The reservoir is closed by caps which are positioned horizontally at both ends of the reservoir. The reservoir is crossed through its longitudinal and median axis by a shaft, turned by an appropriate motor, metal disks having ridges or corrugations on both sides being arranged around the shaft. These disks provide a greater surface area on which to expose the blood to oxygen than is provided by cylinder type apparatus. During use of the standard equipment, the blood enters the inside of the reservoir through a lower inlet. Heat exchangers are also used to control the temperature of the blood flowing into the reservoir. In this process, the blood occupies approximately one-third of the inner volume of the reservoir. A horizonal tube is also provided in the upper inner part of the reservoir which crosses the; reservoir longitudinally and has a number of orifices through which the oxygen is introduced into the reservoir.
Once the inner shaft of the oxygenator begins to turn, along with the inner metallic disks which are partially submerged in the blood, the drag action of the attached disks causes the surfaces of the disks to pick up a film of blood. The blood is then carried by the disks to the upper part of the reservoir where a blood/oxygen contact occurs resulting in the oxygenation of the blood. Once the blood has been oxygenated, it leaves the reservoir and is returned to the patient.
However, there are several drawbacks in the use of this equipment. Because the equipment must be thoroughly cleaned and sterilized after each use to avoid the risk that the equipment may be contaminated with blood-borne pathogens that could be transferred from one surgical operation to the next, the cleaning process used between surgeries is time-consuming and complex, resulting in significant equipment down-time after each use.
Another drawback is that the equipment is relatively large in size, which results in a large quantity of blood being stored in the reservoir during surgery. Moreover, the disk oxygenator functions as a centrifugal pump which tends to keep the oxygen away from the middle of the disks. Thus, the blood is not always wholly or uniformly oxygenated because the blood closest to the shaft receives less oxygen.
A further drawback to using the conventional disk oxygenators is that a very elaborate system is needed to control the level of blood inside the reservoir. An elaborate system is also needed to recapture the blood remaining at the end of the surgery.
Thus, an object of the present invention is to provide an improved disk oxygenator which essentially eliminates the risk of contamination from one surgical procedure to the next surgical procedure. It is also an object of the present invention to reduce or eliminate the extensive labor needed to assemble and disassemble the equipment in order to clean and sterilize the disk oxygenation equipment after surgery. It is a further object of the present invention to provide a blood oxygenator that is smaller in size so that less blood is stored inside the reservoir during surgery. Still further objects of the invention include greater gas transfer control, easier control of the blood level inside the oxygenator and easier recapture of the blood remaining at the end of surgery.